Hairy Evening Primrose

Herbs erect, biennial, with taproot and basal rosette. Stems 50-200 cm tall, simple or sparsely branched, exclusively densely strigillose, or sometimes with few subappressed or spreading pustulate-based hairs or few glandular hairs on floral tube. Leaves gray-green, with prominent pale or red veins, especially abaxially, sessile; rosette blade 10-30 × 1.2-4(-5) cm; cauline blade narrowly lanceolate or oblanceolate to elliptic, 5-20 × 1-2.5(-4) cm, base obtuse to attenuate, margin conspicuously dentate, apex acute. Inflorescence a dense unbranched spike. Flowers open near sunset; floral tube 2.3-4.4 cm. Sepals 9-18 mm, with free tips 0.5-3 mm, apical, erect. Petals yellow to pale yellow, 7-20 mm. Anthers 4-10 mm; pollen ca. 50% fertile. Ovary densely strigillose; stigma surrounded by anthers. Capsules grayish green, lanceoloid, 2-4.3 cm, sessile. Seeds in two rows per locule, brown to nearly black, 1-2 mm, angled, irregularly pitted. Fl. Jul-Sep, fr. Aug-Oct. 2n = 14, permanent translocation heterozygote; self-compatible, autogamous, often cleistogamous.

Heilongjiang, Jilin, Liaoning [native to EC North America; naturalized in Japan, Russia (Far East), and widely in S Africa, Asia, Europe, and S South America].

Open disturbed sites, seasonally moist but often somewhat dryer sites than O. biennis and O. parviflora; near sea level to 1200 m.